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Re: Tyrannosaur Arm Capabilities

Jaime A. Headden wrote:
<We can guess that a tyrannosaur would be unable to sit on a nest, by
factor of the size of its pubis. But the chest was not as projecting,
or blunt, but I'm not proposing it "breasted" its nest as some birds.
Rather, that the mound-building depicted in PDW (Paul, 1988) next to a
tyrannosaur (*Gorgosaurus libratus*) would serve better, and that the
arms, if the animal breast the mound, would have served to move
rubbish, dirt, and other flotsam about to serve to incubate her (or
his) little future prodigies.
  Imagine taking a spreading pronged-hook device (much like a
tyrannosaur's hand) and latch onto a branch, then simply drag it to
the mound, stuff it in, and you have incubator material. Pat the dirt
on (with the fingers next to each other rather than spreading), and in
a while, you have a nice little cassowary-like mound.>
    Why did you start by rejecting the notion that it "breasted" the nest?
Its cousins oviraptor and Cock Robin both do/did this.  You moved away from,
dare I say it? - parsimony, with that assumption.
   The simpler assumption is that T rex built an oviraptor style nest, then
put its arms around it, like oviraptor did. This would bring the birds'
favorite incubator, the breast, into contact with the eggs.  Furthermore, it
would align the arm feathers around the nest or hatchlings, the way that
oviraptor, Caudipteryx, Protarchaeopteryx and modern birds could/can do.
These wing feathers are indespensible for offspring protection in modern
eagles, gulls, ostriches and quail, so why assume there was no use for them in
T rex?
   A crude calculation tells me that T rex's arm span was a bit larger than
oviraptors', so a nest of twenty or so ostrich-sized eggs could be covered and
incubated breast-foremost, in the good old fashioned way.
    Regarding two clawed hand used for nesting - yes, there are modern birds
that dig nest scrapes with their hands, feathers and all (whether they use
their newly re-popularized wing claws or not, I don't know - see earlier posts
on this list).  It seems to me that theropod clawed hands my well have had
primary uses in nest scraping and chick rearing.  That certainly seems to be
the case for oviraptor.
    Tom Hopp